(a) Field of the Invention
The present invention relates to a magnetic bubble memory module and particularly to a magnetic bubble memory module which is suitable for thinning and miniaturizing its body lowering consumption and ameliorating efficiency of composition.
(b) Description of the Prior Art
The magnetic bubble memory module realized in these years has the structure wherein an X-coil and a Y-coil for generating a revolving magnetic field which are respectively composed of square solenoid coils having non-symmetric structures with each other are respectively inserted to E-like substrates made of ceramic, synthetic resin or the like mounting a magnetic bubble memory chip and are arranged at a right angle with each other. The X-coil and the Y-coil must be provided around not only a magnetic bubble memory chip but also a substrate which is far larger than the chip. Thus, the length from one end of each coil to the other end thereof is made longer and thus the driving voltage and the power consumption are made larger. Further, the X-coil and the Y-coil supply a uniform and stable in-plane revolving magnetic field to the magnetic bubble memory chips and thus respectively require a uniform inductor balance. Thus, these coil forms are respectively required to have non-symmetric structures which are different from each other and to have large structures. Moreover, these coils respectively have the structure wherein there are arranged on the outside surfaces of the X-coil and the Y-coil a pair of permanent magnet plates for supplying vertical bias magnetic fields to each magnetic bubble memory chip and the plates for homogenizing their magnetic fields and these peripheral portions are covered with resin molds. Accordingly, their lamination thicknesses in the vertical direction are made larger and this enlargement has been made to be an obstacle to requirements for thinning and miniaturizing a magnetic bubble memory module.
As the closest prior art to the present invention of which the present inventors are aware, it is possible to cite the invention of U.S. Pat. No. 4,165,535. This specification discloses a structure of a picture frame core surrounding a chip and a conducting box for reflecting a magnetic field completely surrounding the core and the chip. However, it does not disclose more concrete structure than the above any more. For example, it is theoretically impossible to carry out electrical connection to a chip completely surrounded by a conductor case from the outside of the conductor case without short-circuiting with the conductor case. Further, it does not clearly disclose the method of mounting a permanent magnet, a plate for homogenizing a magnetic field, a bias coil and the like. Accordingly, the disclosure is apparently insufficient to be considered as a hint for trying to realize the present invention. Namely, as a result, the embodiment of the present invention just happens to coincide with the disclosure of the abovestated specification in the respect of employing a picture frame core for the embodiment of the present invention.